1. Field of the Invention
The present invention relates to a method for manufacturing a gallium nitride compound semiconductor, and in particular to a light emitting element with improved light emitting efficiency and a method of realizing such.
2. Description of the Related Art
In recent years, AlGaN and AlGaN/GaN quantum well superlattices (MQW) or the like have come to be known as materials for light emitting elements, particularly as materials for elements emitting light in the ultraviolet band. Typically, these materials are formed on a sapphire substrate, and dislocations are present due to lattice mismatch of an order of 108˜109/cm2.
At a dislocation, an electron and a hole, which are the carriers, recombine without emitting light (non-luminous recombination). Because of this, as the dislocation density increases, the light emitting efficiency of a light emitting element in general decreases.
FIG. 4 schematically shows the band gap Eg of a material for a light emitting element. As shown, when there is a spatial fluctuation in the band gap of the light emitting element material, light emission occurs only at the locations where the band gap is narrow (gap “a” in the figure). Therefore, if the density of the light emitting points based on the spatial fluctuation of the band gap can be set to exceed the density of dislocations in the light emitting element materials, it is possible to obtain a percentage of the luminous recombination occurring at the points where the band gap is narrow which is higher than the percentage of the non-luminous recombination of an electron and a hole at the dislocations (gap “b” in the figure), and, therefore, degradation in the light emitting efficiency can be inhibited.